/*
 * HISILICON SoC specific OPP wrapper function
 *
 * Copyright (C) 2014 Hisilicon Technologies Co., Ltd.  All rights reserved. 
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/cpufreq.h>
#include <linux/device.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/rcupdate.h>
#include <linux/version.h>
#include "opp.h"

#include "hi_opp_data.h"
#include "hipm.h"
#include "hi_drv_pmoc.h"

/*
 * Internal data structure organization with the OPP layer library is as
 * follows:
 * dev_opp_list (root)
 *	|- device 1 (represents voltage domain 1)
 *	|	|- opp 1 (availability, freq, voltage)
 *	|	|- opp 2 ..
 *	...	...
 *	|	`- opp n ..
 *	|- device 2 (represents the next voltage domain)
 *	...
 *	`- device m (represents mth voltage domain)
 * device 1, 2.. are represented by dev_opp structure while each opp
 * is represented by the opp structure.
 */

/**
 * struct opp - Generic OPP description structure
 * @node:	opp list node. The nodes are maintained throughout the lifetime
 *		of boot. It is expected only an optimal set of OPPs are
 *		added to the library by the SoC framework.
 *		RCU usage: opp list is traversed with RCU locks. node
 *		modification is possible realtime, hence the modifications
 *		are protected by the dev_opp_list_lock for integrity.
 *		IMPORTANT: the opp nodes should be maintained in increasing
 *		order.
 * @available:	true/false - marks if this OPP as available or not
 * @rate:	Frequency in hertz
 * @u_volt:	Nominal voltage in microvolts corresponding to this OPP
 * @dev_opp:	points back to the device_opp struct this opp belongs to
 *
 * This structure stores the OPP information for a given device.
 */
struct opp
{
    struct list_head node;

    bool    available;
    unsigned long rate;
    unsigned long u_volt;

    struct device_opp *dev_opp;
};

/**
 * struct device_opp - Device opp structure
 * @node:	list node - contains the devices with OPPs that
 *		have been registered. Nodes once added are not modified in this
 *		list.
 *		RCU usage: nodes are not modified in the list of device_opp,
 *		however addition is possible and is secured by dev_opp_list_lock
 * @dev:	device pointer
 * @head:	notifier head to notify the OPP availability changes.
 * @opp_list:	list of opps
 *
 * This is an internal data structure maintaining the link to opps attached to
 * a device. This structure is not meant to be shared to users as it is
 * meant for book keeping and private to OPP library
 */
struct device_opp
{
    struct list_head node;

    struct device *     dev;
    struct srcu_notifier_head head;
    struct list_head    opp_list;
};

/*
 * The root of the list of all devices. All device_opp structures branch off
 * from here, with each device_opp containing the list of opp it supports in
 * various states of availability.
 */
static LIST_HEAD(dev_opp_list);

/* Lock to allow exclusive modification to the device and opp lists */
static DEFINE_MUTEX(dev_opp_list_lock);

/**
 * find_device_opp() - find device_opp struct using device pointer
 * @dev:	device pointer used to lookup device OPPs
 *
 * Search list of device OPPs for one containing matching device. Does a RCU
 * reader operation to grab the pointer needed.
 *
 * Returns pointer to 'struct device_opp' if found, otherwise -ENODEV or
 * -EINVAL based on type of error.
 *
 * Locking: This function must be called under rcu_read_lock(). device_opp
 * is a RCU protected pointer. This means that device_opp is valid as long
 * as we are under RCU lock.
 */
static struct device_opp *find_device_opp(struct device *dev)
{
    struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);

    if (unlikely(IS_ERR_OR_NULL(dev)))
    {
        HI_ERR_PM("%s: Invalid parameters\n", __func__);
        return ERR_PTR(-EINVAL);
    }

    list_for_each_entry_rcu(tmp_dev_opp, &dev_opp_list, node)
    {
        if (tmp_dev_opp->dev == dev)
        {
            dev_opp = tmp_dev_opp;
            break;
        }
    }

    return dev_opp;
}

/**
 * opp_get_voltage() - Gets the voltage corresponding to an available opp
 * @opp:	opp for which voltage has to be returned for
 *
 * Return voltage in micro volt corresponding to the opp, else
 * return 0
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. This means that opp which could have been fetched by
 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
 * under RCU lock. The pointer returned by the opp_find_freq family must be
 * used in the same section as the usage of this function with the pointer
 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
 * pointer.
 */
unsigned long opp_get_voltage(struct opp *opp)
{
    struct opp *tmp_opp;
    unsigned long v = 0;

    tmp_opp = rcu_dereference(opp);
    if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
    {
        HI_ERR_PM("%s: Invalid parameters\n", __func__);
    }
    else
    {
        v = tmp_opp->u_volt;
    }

    return v;
}

/**
 * opp_get_freq() - Gets the frequency corresponding to an available opp
 * @opp:	opp for which frequency has to be returned for
 *
 * Return frequency in hertz corresponding to the opp, else
 * return 0
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. This means that opp which could have been fetched by
 * opp_find_freq_{exact,ceil,floor} functions is valid as long as we are
 * under RCU lock. The pointer returned by the opp_find_freq family must be
 * used in the same section as the usage of this function with the pointer
 * prior to unlocking with rcu_read_unlock() to maintain the integrity of the
 * pointer.
 */
unsigned long opp_get_freq(struct opp *opp)
{
    struct opp *tmp_opp;
    unsigned long f = 0;

    tmp_opp = rcu_dereference(opp);
    if (unlikely(IS_ERR_OR_NULL(tmp_opp)) || !tmp_opp->available)
    {
        HI_ERR_PM("%s: Invalid parameters\n", __func__);
    }
    else
    {
        f = tmp_opp->rate;
    }

    return f;
}

/**
 * opp_get_opp_count() - Get number of opps available in the opp list
 * @dev:    device for which we do this operation
 *
 * This function returns the number of available opps if there are any,
 * else returns 0 if none or the corresponding error value.
 *
 * Locking: This function must be called under rcu_read_lock(). This function
 * internally references two RCU protected structures: device_opp and opp which
 * are safe as long as we are under a common RCU locked section.
 */
int opp_get_opp_count(struct device *dev)
{
    struct device_opp *dev_opp;
    struct opp *temp_opp;
    int count = 0;

    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        int r = PTR_ERR(dev_opp);
        HI_ERR_PM( "OPP not found (%d)\n", __func__);
        return r;
    }

    list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node)
    {
        if (temp_opp->available)
        {
            count++;
        }
    }

    return count;
}

/**
 * opp_find_freq_exact() - search for an exact frequency
 * @dev:		device for which we do this operation
 * @freq:		frequency to search for
 * @available:		true/false - match for available opp
 *
 * Searches for exact match in the opp list and returns pointer to the matching
 * opp if found, else returns ERR_PTR in case of error and should be handled
 * using IS_ERR.
 *
 * Note: available is a modifier for the search. if available=true, then the
 * match is for exact matching frequency and is available in the stored OPP
 * table. if false, the match is for exact frequency which is not available.
 *
 * This provides a mechanism to enable an opp which is not available currently
 * or the opposite as well.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct opp *opp_find_freq_exact(struct device *dev, unsigned long freq,
                                bool available)
{
    struct device_opp *dev_opp;
    struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);

    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        int r = PTR_ERR(dev_opp);
        HI_ERR_PM( "OPP not found (%d)\n", __func__);
        return ERR_PTR(r);
    }

    list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node)
    {
        if ((temp_opp->available == available)
            && (temp_opp->rate == freq))
        {
            opp = temp_opp;
            break;
        }
    }

    return opp;
}

/**
 * opp_find_freq_ceil() - Search for an rounded ceil freq
 * @dev:	device for which we do this operation
 * @freq:	Start frequency
 *
 * Search for the matching ceil *available* OPP from a starting freq
 * for a device.
 *
 * Returns matching *opp and refreshes *freq accordingly, else returns
 * ERR_PTR in case of error and should be handled using IS_ERR.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct opp *opp_find_freq_ceil(struct device *dev, unsigned long *freq)
{
    struct device_opp *dev_opp;
    struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);

    if (!dev || !freq)
    {
        HI_ERR_PM("%s: Invalid argument freq=%p\n", __func__, freq);
        return ERR_PTR(-EINVAL);
    }

    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        return opp;
    }

    list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node)
    {
        if (temp_opp->available && (temp_opp->rate >= *freq))
        {
            opp = temp_opp;
            *freq = opp->rate;
            break;
        }
    }

    return opp;
}

/**
 * opp_find_freq_floor() - Search for a rounded floor freq
 * @dev:	device for which we do this operation
 * @freq:	Start frequency
 *
 * Search for the matching floor *available* OPP from a starting freq
 * for a device.
 *
 * Returns matching *opp and refreshes *freq accordingly, else returns
 * ERR_PTR in case of error and should be handled using IS_ERR.
 *
 * Locking: This function must be called under rcu_read_lock(). opp is a rcu
 * protected pointer. The reason for the same is that the opp pointer which is
 * returned will remain valid for use with opp_get_{voltage, freq} only while
 * under the locked area. The pointer returned must be used prior to unlocking
 * with rcu_read_unlock() to maintain the integrity of the pointer.
 */
struct opp *opp_find_freq_floor(struct device *dev, unsigned long *freq)
{
    struct device_opp *dev_opp;
    struct opp *temp_opp, *opp = ERR_PTR(-ENODEV);

    if (!dev || !freq)
    {
        HI_ERR_PM("%s: Invalid argument freq=%p\n", __func__, freq);
        return ERR_PTR(-EINVAL);
    }

    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        return opp;
    }

    list_for_each_entry_rcu(temp_opp, &dev_opp->opp_list, node)
    {
        if (temp_opp->available)
        {
            /* go to the next node, before choosing prev */
            if (temp_opp->rate > *freq)
            {
                break;
            }
            else
            {
                opp = temp_opp;
            }
        }
    }
    if (!IS_ERR(opp))
    {
        *freq = opp->rate;
    }

    return opp;
}

/**
 * opp_add()  - Add an OPP table from a table definitions
 * @dev:	device for which we do this operation
 * @freq:	Frequency in Hz for this OPP
 * @u_volt:	Voltage in uVolts for this OPP
 *
 * This function adds an opp definition to the opp list and returns status.
 * The opp is made available by default and it can be controlled using
 * opp_enable/disable functions.
 *
 * Locking: The internal device_opp and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks
 * to keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex cannot be locked.
 */
int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
{
    struct device_opp *dev_opp = NULL;
    struct opp *opp, *new_opp;
    struct list_head *head;

    /* allocate new OPP node */
    new_opp = kzalloc(sizeof(struct opp), GFP_KERNEL);
    if (!new_opp)
    {
        HI_WARN_PM("%s: Unable to create new OPP node\n", __func__);
        return -ENOMEM;
    }

    /* Hold our list modification lock here */
    mutex_lock(&dev_opp_list_lock);

    /* Check for existing list for 'dev' */
    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        /*
         * Allocate a new device OPP table. In the infrequent case
         * where a new device is needed to be added, we pay this
         * penalty.
         */
        dev_opp = kzalloc(sizeof(struct device_opp), GFP_KERNEL);
        if (!dev_opp)
        {
            mutex_unlock(&dev_opp_list_lock);
            kfree(new_opp);
            HI_WARN_PM("%s: Unable to create device OPP structure\n",
                       __func__);
            return -ENOMEM;
        }

        dev_opp->dev = dev;
        srcu_init_notifier_head(&dev_opp->head);
        INIT_LIST_HEAD(&dev_opp->opp_list);

        /* Secure the device list modification */
        list_add_rcu(&dev_opp->node, &dev_opp_list);
    }

    /* populate the opp table */
    new_opp->dev_opp = dev_opp;
    new_opp->rate = freq;
    new_opp->u_volt = u_volt;
    new_opp->available = true;

    /* Insert new OPP in order of increasing frequency */
    head = &dev_opp->opp_list;
    list_for_each_entry_rcu(opp, &dev_opp->opp_list, node)
    {
        if (new_opp->rate < opp->rate)
        {
            break;
        }
        else
        {
            head = &opp->node;
        }
    }

    list_add_rcu(&new_opp->node, head);
    mutex_unlock(&dev_opp_list_lock);

    /*
     * Notify the changes in the availability of the operable
     * frequency/voltage list.
     */
    srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp);
    return 0;
}

/**
 * opp_set_availability() - helper to set the availability of an opp
 * @dev:		device for which we do this operation
 * @freq:		OPP frequency to modify availability
 * @availability_req:	availability status requested for this opp
 *
 * Set the availability of an OPP with an RCU operation, opp_{enable,disable}
 * share a common logic which is isolated here.
 *
 * Returns -EINVAL for bad pointers, -ENOMEM if no memory available for the
 * copy operation, returns 0 if no modifcation was done OR modification was
 * successful.
 *
 * Locking: The internal device_opp and opp structures are RCU protected.
 * Hence this function internally uses RCU updater strategy with mutex locks to
 * keep the integrity of the internal data structures. Callers should ensure
 * that this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 */
static int opp_set_availability(struct device *dev, unsigned long freq,
                                bool availability_req)
{
    struct device_opp *tmp_dev_opp, *dev_opp = ERR_PTR(-ENODEV);
    struct opp *new_opp, *tmp_opp, *opp = ERR_PTR(-ENODEV);
    int r = 0;

    /* keep the node allocated */
    new_opp = kmalloc(sizeof(struct opp), GFP_KERNEL);
    if (!new_opp)
    {
        HI_WARN_PM("%s: Unable to create OPP\n", __func__);
        return -ENOMEM;
    }

    mutex_lock(&dev_opp_list_lock);

    /* Find the device_opp */
    list_for_each_entry(tmp_dev_opp, &dev_opp_list, node)
    {
        if (dev == tmp_dev_opp->dev)
        {
            dev_opp = tmp_dev_opp;
            break;
        }
    }
    if (IS_ERR(dev_opp))
    {
        r = PTR_ERR(dev_opp);
        HI_WARN_PM("%s: Device OPP not found (%d)\n", __func__, r);
        goto unlock;
    }

    /* Do we have the frequency? */
    list_for_each_entry(tmp_opp, &dev_opp->opp_list, node)
    {
        if (tmp_opp->rate == freq)
        {
            opp = tmp_opp;
            break;
        }
    }
    if (IS_ERR(opp))
    {
        r = PTR_ERR(opp);
        goto unlock;
    }

    /* Is update really needed? */
    if (opp->available == availability_req)
    {
        goto unlock;
    }

    /* copy the old data over */
    *new_opp = *opp;

    /* plug in new node */
    new_opp->available = availability_req;

    list_replace_rcu(&opp->node, &new_opp->node);
    mutex_unlock(&dev_opp_list_lock);
    synchronize_rcu();

    /* Notify the change of the OPP availability */
    if (availability_req)
    {
        srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ENABLE,
                                 new_opp);
    }
    else
    {
        srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_DISABLE,
                                 new_opp);
    }

    /* clean up old opp */
    new_opp = opp;
    goto out;

unlock:
    mutex_unlock(&dev_opp_list_lock);
out:
    kfree(new_opp);
    return r;
}

/**
 * opp_enable() - Enable a specific OPP
 * @dev:	device for which we do this operation
 * @freq:	OPP frequency to enable
 *
 * Enables a provided opp. If the operation is valid, this returns 0, else the
 * corresponding error value. It is meant to be used for users an OPP available
 * after being temporarily made unavailable with opp_disable.
 *
 * Locking: The internal device_opp and opp structures are RCU protected.
 * Hence this function indirectly uses RCU and mutex locks to keep the
 * integrity of the internal data structures. Callers should ensure that
 * this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 */
int opp_enable(struct device *dev, unsigned long freq)
{
    return opp_set_availability(dev, freq, true);
}

/**
 * opp_disable() - Disable a specific OPP
 * @dev:	device for which we do this operation
 * @freq:	OPP frequency to disable
 *
 * Disables a provided opp. If the operation is valid, this returns
 * 0, else the corresponding error value. It is meant to be a temporary
 * control by users to make this OPP not available until the circumstances are
 * right to make it available again (with a call to opp_enable).
 *
 * Locking: The internal device_opp and opp structures are RCU protected.
 * Hence this function indirectly uses RCU and mutex locks to keep the
 * integrity of the internal data structures. Callers should ensure that
 * this function is *NOT* called under RCU protection or in contexts where
 * mutex locking or synchronize_rcu() blocking calls cannot be used.
 */
int opp_disable(struct device *dev, unsigned long freq)
{
    return opp_set_availability(dev, freq, false);
}

#ifdef CONFIG_CPU_FREQ

/**
 * opp_init_cpufreq_table() - create a cpufreq table for a device
 * @dev:	device for which we do this operation
 * @table:	Cpufreq table returned back to caller
 *
 * Generate a cpufreq table for a provided device- this assumes that the
 * opp list is already initialized and ready for usage.
 *
 * This function allocates required memory for the cpufreq table. It is
 * expected that the caller does the required maintenance such as freeing
 * the table as required.
 *
 * Returns -EINVAL for bad pointers, -ENODEV if the device is not found, -ENOMEM
 * if no memory available for the operation (table is not populated), returns 0
 * if successful and table is populated.
 *
 * WARNING: It is  important for the callers to ensure refreshing their copy of
 * the table if any of the mentioned functions have been invoked in the interim.
 *
 * Locking: The internal device_opp and opp structures are RCU protected.
 * To simplify the logic, we pretend we are updater and hold relevant mutex here
 * Callers should ensure that this function is *NOT* called under RCU protection
 * or in contexts where mutex locking cannot be used.
 */
int opp_init_cpufreq_table(struct device *                  dev,
                           struct cpufreq_frequency_table **table)
{
    struct device_opp *dev_opp;
    struct opp *opp;
    struct cpufreq_frequency_table *freq_table;
    int i = 0;

    /* Pretend as if I am an updater */
    mutex_lock(&dev_opp_list_lock);

    dev_opp = find_device_opp(dev);
    if (IS_ERR(dev_opp))
    {
        int r = PTR_ERR(dev_opp);
        mutex_unlock(&dev_opp_list_lock);
        HI_ERR_PM("%s: Device OPP not found (%d)\n", __func__, r);
        return r;
    }

    freq_table = kzalloc(sizeof(struct cpufreq_frequency_table) *
                         (opp_get_opp_count(dev) + 1), GFP_KERNEL);
    if (!freq_table)
    {
        mutex_unlock(&dev_opp_list_lock);
        HI_WARN_PM("%s: Unable to allocate frequency table\n",
                   __func__);
        return -ENOMEM;
    }

    list_for_each_entry(opp, &dev_opp->opp_list, node)
    {
        if (opp->available)
        {
            freq_table[i].frequency = opp->rate;
            i++;
        }
    }
    mutex_unlock(&dev_opp_list_lock);

    freq_table[i].frequency = CPUFREQ_TABLE_END;

    *table = &freq_table[0];

    return 0;
}

/**
 * opp_free_cpufreq_table() - free the cpufreq table
 * @dev:	device for which we do this operation
 * @table:	table to free
 *
 * Free up the table allocated by opp_init_cpufreq_table
 */
void opp_free_cpufreq_table(struct device *                 dev,
                            struct cpufreq_frequency_table **table)
{
    if (!table)
    {
        return;
    }

    kfree(*table);
    *table = NULL;
}

#endif      /* CONFIG_CPU_FREQ */

/**
 * opp_get_notifier() - find notifier_head of the device with opp
 * @dev:	device pointer used to lookup device OPPs.
 */
struct srcu_notifier_head *opp_get_notifier(struct device *dev)
{
    struct device_opp *dev_opp = find_device_opp(dev);

    if (IS_ERR(dev_opp))
    {
        return ERR_CAST(dev_opp); /* matching type */
    }

    return &dev_opp->head;
}

/* Temp variable to allow multiple calls */
static u8 __initdata hi_table_init;

/**
 * hi_init_opp_table() - Initialize opp table as per the CPU type
 * @opp_def:		opp default list for this silicon
 * @opp_def_size:	number of opp entries for this silicon
 *
 * Register the initial OPP table with the OPP library based on the CPU
 * type. This is meant to be used only by SoC specific registration.
 */
int __init hi_init_opp_table(struct hi_opp_def *opp_def,
                             u32    opp_def_size)
{
    int i, r;

    if (!opp_def || !opp_def_size)
    {
        HI_ERR_PM("%s: invalid params!\n", __func__);
        return -EINVAL;
    }

    /*
     * Initialize only if not already initialized even if the previous
     * call failed, because, no reason we'd succeed again.
     */
    if (hi_table_init)
    {
        return -EEXIST;
    }

    hi_table_init = 1;

    /* Lets now register with OPP library */
    for (i = 0; i < opp_def_size; i++)
    {
        r = opp_add(&mpu_dev, opp_def->freq, opp_def->u_volt);
        if (r)
        {
            HI_ERR_PM("%s: add OPP %ld failed for [%d] "
                      "result=%d\n",
                      __func__, opp_def->freq,
                      i, r);
        }
        else
        {
            if (!opp_def->default_available)
            {
                r = opp_disable(&mpu_dev, opp_def->freq);
            }

            if (r)
            {
                HI_ERR_PM("%s: disable %ld failed for"
                          "[%d] result=%d\n",
                          __func__, opp_def->freq,
                          i, r);
            }
        }

        opp_def++;
    }

    return 0;
}
